In many industrial adhesive bonding operations an adhesion promoter is applied to a surface to improve bonding of the adhesive to the surface of the substrate. Typical adhesion promoters are delivered dissolved, or dispersed, in an organic solvent. Organic solvents are used because many have low vapor pressures and volatilize away rapidly after application to the substrate. The solvent needs to be removed before application of the adhesive to facilitate bonding of the adhesive to the substrate. Organic solvents are also chosen because the adhesion promoting components typically can be dissolved or dispersed in an organic solvent. The use of organic solvents can result in their release into the environment. Alternatively, the use of organic solvents may require expensive ventilation and capturing equipment to reduce the risk of unacceptable human exposure or contamination of the environment.
For the abovementioned reasons there is considerable pressure to replace organic solvents in adhesion promoting systems with water. Adhesion promoters dissolved in or dispersed in water are known; see Gimvang United States Patent Publication 2009/0108231 and Braun et al. United States Patent Publication 2007/0187028. The use of water presents its own set of problems, including problems with solubility of the ingredients of the adhesion promoter in water and waters relatively high vapor pressure which can result in slow evaporation of water off of a substrate surface. This slow evaporation can slow down industrial processes. In many process the desire is to run the processes as fast as possible. Some of the known processes utilizing water based adhesion promoters require special dispensers, complex formulations or process conditions. Water based adhesion promoters can demonstrate poor wetting properties on certain surfaces:
What is needed is a composition which is not complex, avoids the use of organic solvents, can be applied using standard application processes and equipment, accommodate standard industrial processing speeds, wets surfaces well and is environmentally friendly. What is further needed are processes for using such compositions to promote adhesion of adhesives to surfaces.